Chapter 5, Problem 5F.5AST

Interpretation Introduction

Interpretation:

The osmotic pressure of $\text{3}\text{.0}\text{g}$ polystyrene dissolved in enough benzene produces $\text{150}\text{mL}$ of solution is $\text{1}\text{.21}\text{kPa}$ at ${\text{25}}^{\text{°}}\text{C}$.  The average molar mass of sample of polystyrene has to be calculated.

Concept Introduction:

By using the Osmometric method, the molar mass of solute can be calculated as follows:

Step-1: The observed osmotic pressure has to be converted into solute molar concentration, $\text{c}$ in the form of

  $\text{c}\text{=}\frac{\text{Π}}{\text{iRT}}$

Step-2: The amount of solute (in moles) in the solution is calculated by multiplying the molar concentration of solute by the volume of solution.

  ${\text{n}}_{\text{solute}}\text{=}{\text{c}}_{\text{solute}}\text{×}\text{V}$

Step-3: The molar mass of the solute is calculated by dividing the given mass of solute (in grams) by the calculated amount in moles.

  ${\text{M}}_{\text{solute}}\text{=}\frac{{\text{m}}_{\text{solute}}}{{\text{n}}_{\text{solute}}}$